When a stimulant-dependent individual abstains from stimulant use, withdrawal symptoms, including depression, fatigue, insomnia, and loss of appetite, reflects a drop in neurotransmitter levels in the brain.
Someone's blood alcohol concentration can continue to rise even while he or she is unconscious.
Methadone withdrawal can be even more severe than morphine or heroin withdrawal and can last for several weeks or more.
Methadone maintenance treatment is a multi-billion dollar global industry which is very profitable for drug companies and clinics.